The present disclosure relates to a magnetically driven micropump for handling small fluid volumes. In particular, the present disclosure related to a micropump including a magnetically actuated membrane to transfer fluids.
The field of microfluidics generally encompasses handling very small fluid volumes on the order of several nanoliters. Microfluidics has increasingly important applications in such fields as life sciences and chemical analysis. Microfluidics devices, also known as micromechanical systems (MEMS), include devices for fluid control, fluid measurement, medical testing, DNA and protein analysis, in vivo drug delivery, and other biomedical applications.
Typical fluid flow rates of micropumps range from approximately 0.1 microliter per minute to several (80-180) milliters per minute. Flow rates on this order are useful in applications such as disposable micro total analysis systems (μTAS) or lab-on-a-chip (LOC) for chemical and biological analysis, point of care testing (POCT) for medical diagnostic testing, implantable drug delivery systems for medications (such as insulin) requiring a fine degree of regulation and precise control, and cardiology systems for blood transport and pressurization.
Since most of MEMS processing techniques evolved from microelectronics, the first silicon micropump was based on a piezoelectric actuation of a thin membrane in 1980s primarily for use in the controlled insulin delivery systems. This work demonstrated the feasibility of silicon-based micropump and inspired extensive research on silicon micropumps. Also, several commercially available implantable silicon micropumps were reported for insulin delivery and therapeutic agents dispensing through pharmaceutical and clinical therapy fields.
Recently, a number of polymeric materials and new microfabrication techniques, such as soft lithography, microstereolithography, micromolding and polymeric surface micromachining, have been investigated and developed for a growing trend of low cost, integrated and miniaturized disposable μTAS applications. Many polymeric materials including plastics and elastomers have been increasingly incorporated into other microdevices as substrates, structural membranes, and functional membranes due to their excellent mechanical properties, good chemical resistance, and low fabrication cost. Among the most popular polymers, polydimethylsiloxane (PDMS) has been extensively utilized in microfluidic devices because of excellent biocompatibility, simple fabrication process (molding and reversible bonding) and optical transparency (facilitating monitoring and interrogating) as well as elasticity (good sealing and connecting).
Silicon-based and plastic-based valveless micropumps are taken as an example to compare with polymer-based micropump. The fabrication process of the silicon-based micropump involved three subsequent Deep Reactive Ion Etching (DRIE) steps and one silicon-glass anodic bonding step while LIGA, microinjection, or hot embossing molding and multiple thin plate assembly with adhesives or bolts was involved for the plastic pumps. On the other hand, for a PDMS-based micropump only multilayer soft lithography processes and PDMS-PDMS bonding techniques are required. From the fabrication cost point of view, a PDMS-based micropump is considerably lower than the former two types of micropumps.
Furthermore, the main challenge of the plastic micropump is the high fluid leakage due to the surface roughness of the thin plastic layers. Bolt-assembly makes matters even worse because the stress is concentrated on the interface between the layers where bolts were connected. The adhesive bonding also tends to contribute to blockage of the microstructures. Therefore, the PDMS is a practical (short process time and low cost) material for micropumps.